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<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
</head>
<body>
    <div id="wrap"></div>

    <p class="goudan"></p>
    <p class="goudan"></p>
    <p class="goudan"></p>

    <script>
    
        // let oWrap = document.getElementById("wrap");
        // console.dir(oWrap);
        // oWrap.id = "g456";
        // oWrap.title = "凯哥";

        // let aP = document.getElementsByClassName("goudan");

        // let oP = aP[0];
        // console.log(aP[0] === oP);
        // oP.className = "dachui";
        // console.log(aP[0] === oP);
        // oP.title = "pppp";


        // aP[0].className = "dachui";
        // aP[0].innerHTML = "123";


        let aP = document.querySelectorAll(".goudan");
        console.log(aP);

        aP[0].className = "dachui";
        console.log(aP);

    </script>
</body>
</html>